Merkur XR4Ti ??

[twinturbo]

Originally Posted by alga

Hmm, I think the strain on the gearbox depends on the power (torque * rotational speed) being transfered though it, not the weight being moved or anything else. The torque, though, is limited by the grip of the rear tyres, which is directly proportional to the weight on the rear axle. I wonder, what is the practical limit of torque/power that can be put down on the Roadster with semislick tyres like R888?

It has been discussed several times on here that 160-180 bhp is the limit for a Seven type car beyond where there are diminishing returns from extra power. Perhaps that is the limit of typical road tyres with the roadster's weight?

Put the same driveline in a car weighing 45 tones. Will the gearbox survive less well than in a car at .45 tones.

The torque required to accelerate the heavier load is much higher.

TT

[alga]

Originally Posted by twinturbo

Put the same driveline in a car weighing 45 tones. Will the gearbox survive less well than in a car at .45 tones.

Nah, realistically the engine will stall with 45 tonnes. It will not be able to put out enough torque to move the weight. The strain on the gearbox will be limited by the power of the engine if we disregard the impacts on stalling.

The torque required to accelerate the heavier load is much higher.

I'd put it the other way around: the same torque will accelerate the smaller weight quicker. It's plausible that the load cycles on the transmission will be cumulatively shorter on a Roadster, but then again Sierra was most probably someone's docile daily driver, while the Roadster is a throwabout toy if not a race weapon.

Consider a Sierra and a Roaster on a rolling road dyno -- the strain on the gearbox depends solely on the power of the engine that's getting put down through the wheels.

[ih8hardtops]

Wow, Thanks all. Lot's to think about.
"my" T9
1st- 3.36:1
2nd- 1.81:1
3rd- 1.26:1
4th- 1.00:1
5th- 0.82:1
.
Axle ratio- 3.61:1
Final drive- 2.98:1
205/60-15 tires (about 24" tall)

[snapper]

You have the V6 T9 Ford rate this at 155bhp and 155 ft/lbs torque but we know by experience that it will be ok at 180 on the road.
Slicks can kill a gearbox that's not up to the job.
However build the car with what you have to hand you can always upgrade later

[XR4BILL]

I agree with snapper, you can always upgrade later.
My Xr has the T5 from a Mustang (not the best of ratios, but lots available in the scrap yards.) You can also upgrade it to the Cosworth ratios and higher torque specs. (available off E-bay, for approx $450:00US if I remember correctly, I have that info if required.) I Just had to aquire the Turbo Coupe bell housing to mate it to the 2.3L block.
Because I have 2 spare T5 boxes, one will be installed in the kit car.
MC2 racing also does a conversion to convert the Stock XR diff to a Chev LSD type diff for approx $500:00US. (The internals fit into the Xr diff casing.)
The Toyota Supra LSD diff could also be an option. This diff can be made to work in the Xr, so it should be possible to make it fit the Kit car. This diff has a few ratio options I believe.

cheers,

Bill.

[michmark]

I have been working on a Roadster with the Merkur donor. In the US, the 2.3 liter engine was rated at 175 hp (130 kW) and 264.0 nm / 194.7 ft lbs, so I think the T9 could handle most powerplants.

To those using the Merkur diff, be aware that the housing is wider than the Euro spec. SB4 and CP10 will need to be moved accordingly.

Mark Bates

[ih8hardtops]

Seems we have some pretty intelligent people here

Originally Posted by XR4BILL

MC2 racing also does a conversion to convert the Stock XR diff to a Chev LSD type diff for approx $500:00US. (The internals fit into the Xr diff casing.)

cheers,

Bill.

Bill, My son has an almost new aftermarket rebuildable Eaton plate type lsd that uses 26 spline GM axles (was in Chevy Monza) but it's a 2 series carrier. Any idea if it could be used with a spacer on the xr's ring gear? I believe the Eaton into XR swap claims to need a 3 series carrier?? I'll do some searching over at Merkursport. Thanks

Jeff

[XR4BILL]

Jeff, the best option would be to fire off an email to Chris at MC2 Racing. He could tell you exactly what they do.
There is a fair bit of info at the MC2 site as well. Also do a search at the Merkur Forum.
Not sure about what you ask, as I installed a 7.5`Cossie Diff into my XR. Basically a straight swap with some spacers etc. I have 2 stock Xr diffs lying around that I was considering using. I was also thinking about the Supra Diff into the XR and the Cossie Diff into the Kit car.
I will be looking at Diffs later, as I begin the build in the new year.
cheers,
Bill.